Conventional system for preventing a wheel of a motor vehicle from skidding have been known, for example, a system which controls a hydraulic pressure applied to a wheel cylinder of a brake device in accordance with a rotation status of the wheel relative to a threshold value when the vehicle decelerates.
Further, there has been a conventional system for preventing a driving wheel of the vehicle from slipping by controlling a brake force caused by a hydraulic pressure in a wheel cylinder of a brake device of the driving wheel in accordance with a slipping status relative to a threshold value when the vehicle starts to move and accelerates.
These conventional systems, however, require an extra space and extra equipment which raises the cost.
Further, in the system for preventing the vehicle from skidding in which the hydraulic pressure applied to the wheel cylinder of the brake system is controlled, the brake force should preferably be controlled as large as possible within a range in which the wheel does not lock in order to decrease a large force of inertia of the moving vehicle as rapid as possible. On the other hand, in the system for preventing the driving wheel from slipping in which the hydraulic pressure applied to the driving wheel is controlled so that a torque suitably corresponds to an adhesion between the road and tires of the vehicle, the brake force should be varied calmly. That is, since the torque of the driving wheel is smaller than that of the brake, if a large brake force is actuated during an acceleration slip-preventing control of the driving wheel, the driving torque may be excessively decreased and the motor vehicle would not accelerate effectively.
In the conventional acceleration slip-preventing control of the driving wheel, the brake force may be excessively actuated since the brake force is not appropriately controlled.